Intereting Posts

Assigning alternate crossings to closed curves
What is the limit of this sequence involving logs of binomials?
Expressing $2002^{2002}$ as a sum of cubes
Can't understand Second Fundamental Theorem of Calculus
The most common theorems taught in Abstract Algebra
Raising to the power over finite fields ??
Evaluating $ \int \frac{1}{5 + 3 \sin(x)} ~ \mathrm{d}{x} $.
How many ways to do n chose k such that the picks are non-decreasing?
If $x – \lvert x \rvert + \frac{1}{x} – \lvert \frac{1}{x} \rvert = 1$ then $x$ is irrational
Dimension of spheres in sphere bundles
Ring with spectrum homeomorphic to a given topological space
Proof that $3 \mid \left( a^2+b^2 \right)$ iff $3 \mid \gcd \left( a,b\right)$
Prove that $SC=SP$ if and only if $MK=ML.$
Distribution of sums of inverses of random variables uniformly distributed on
Find the steady state temperature of the heat equation

Who invented or used very first the double lined symbols $\mathbb{R},\mathbb{Q},\mathbb{N}$ etc. to represent the real number system, rational number system, natural number system respectively?

- Why are even/odd functions called even/odd?
- Is there a recommended symbol for “equal by abuse of notation”?
- In the history of mathematics, has there ever been a mistake?
- Is it mathematically correct to write $a \bmod n \equiv b$?
- Indian claims finding new cube root formula
- What is the purpose of defining the notion of inflection point?
- What is the primary source of Hilbert's famous “man in the street” statement?
- Why do we assume principal root
- What does the $\prod$ symbol mean?
- Who first defined open sets in terms of neighborhoods?

A Wikipedia page that seems to be relevant:

$\ldots$ blackboard bold in fact originated from the attempt to write bold letters on blackboards in a way that clearly differentiated them from non-bold letters, and then made its way back in print form as a separate style from ordinary bold, possibly starting with the original 1965 edition of Gunning and Rossi’s textbook on complex analysis.

It is sometimes erroneously claimed that Bourbaki introduced the blackboard bold notation, but whereas individual members of the Bourbaki group may have popularized double-striking bold characters on the blackboard, their printed books use ordinary bold $\ldots$

I have no references here, just stories my professor told us. As far as I know, the double lines were not double lines in the beginning, but rather boldened lines, so people wrote R with a slightly thicker vertical line to denote the real numbers.

The laziness of mathematitians and difficulty of writing a bolder line that students will recognise on a blackboard led to professors writing double lines instead of bold lines, and the practice stuck.

- Existence of iid random variables
- CDF of a sum of independent random variables
- A proof that $1=2$. May I know why it’s false?
- An identity involving the Möbius function
- What is this geometric pattern called?
- Is there any difference between mapping and function?
- Find the transitional matrix that would transform this form to a diagonal form.
- Distances between points and polygons
- Limit behavior of a definite integral that depends on a parameter.
- Differentials Definition
- Bipartite graph non-isomorphic to a subgraph of any k-cube
- Prove partial derivatives of uniformly convergent harmonic functions converge to the partial derivative of the limit of the sequence.
- Norm of the sum of projection operators
- Prove that $C_n < 4n^2$ for all n greater than or equal to 1
- The elegant expression in terms of gcd and lcm – algebra – (2)